EFFECT OF PASTEURELLA-MULTOCIDA TOXIN ON IN-VIVO IMMUNE-RESPONSES IN PIGLETS

Atrophic rhinitis is characterized by a lack of an immune response tow ards Pasteurella multocida toxin (Pm-T), The effects of intranasal adm inistration of Pm-T on cellular and T-cell dependent antibody response s of piglets against various other antigens were studied in a 3 by 2 f actorial arrangement of treatments: three levels of challenge with Pm- T (either once; on three consecutive days; or no Pm-T challenge), and with or without simultaneous immunization with a 'cocktail' containing Keyhole limpet haemocyanin (KLH), ovalbumin (OA) and tetanus toroid ( TT). Challenge with Pm-T affected but did not abolish the in vivo humo ral immune response against OA, KLH, or TT, Pigs treated once with Pm- T showed lower total antibody responses, caused by lower IgG responses to the antigens, We found no clear consistent effects of Pm-T on cell ular immune responses to the various T-cell-dependent antigens in vitr o. The lack of immune responsiveness to Pm-T in Pm-T challenged pigs i s discussed, The absence of detectable immune responses does not depen d on a general suppression of the cellular immune system.